In rotary regenerative heat exchange apparatus a mass of heat absorbent element commonly comprised of packed element plates is first positioned in a hot gas passageway to absorb heat from hot gases passing therethrough. After the plates become heated by the hot gases they are moved to a passageway for cooler fluid where the heated plates transmit the absorbed heat to cool air or other fluid passing therethrough.
The heat absorbent plates are carried in a rotor that rotates between hot and cool fluids while housing structure including apertured sector plates at opposite ends of the rotor is adapted to surround the rotor. To prevent leakage and the mingling of the hot and cool fluids, the end edges of the rotor are provided with flexible sealing members that rub against the adjacent parts of the rotor housing to resiliently accommodate a limited amount of "turndown" or other distortion caused by mechanical loading and thermal deformation of the rotor.
To permit turning the rotor freely about its axis, certain minimum clearance space between the rotor and the confronting parts of the rotor housing is required, however, excessive clearance is to be avoided because it will dictate excessive fluid leakage. However, under transient conditions marked by a rapid change of temperature and expansion of the rotor and the rotor housing, excessive leakage may develop and a lower effectiveness will result.
The expansion of the rotor and the adjacent housing structure assumes maximum proportions directly adjacent the inlet for the hot fluid where the temperature is the maximum. An arrangement that compensates for a loss of sealing effectiveness at this, the "hot end" of a rotor, is shown by U.S. Pat. No. 3,786,868 where a plane sector plate is pivoted about a fulcrum carried by the housing. A later U.S. Pat. No. 4,124,063 permitted reduced leakage by providing a sector plate that was forced to arcuately deform in accordance with the thermal deformation being experienced by the rotor. Although such an arrangement may be effective for normal operating conditions, a rapid change of temperature may cause a differential of expansion between the rotor and the rotor housing whereby there will be interference of one with the other causing excessive wear and degradation of abutting surfaces.